none Lysiphlebus; Oigosita; Delphacodes striatella; Dimorphopterus spinolae; KARYOTYPE-; Description; JAPAN-; Karyotype description Aphididae; KARYOTYPE-; JAPAN-; Species descriptions Chromosomes of five Hemipterans (Hemiptera) and two hymenopterans (Hymenoptera) were studied. The chromosome number and the sex mechanism were respectively 2n = 16 ( male , and X-Y type) for Dimorphopterus spinolae (Lygaeidae), 2n = 10 ( female ) for Colopha morikaensis, 2n = 12 ( female ) for Myzocallis kuricola (Aphididae) 2n = 28 ( male , an X-Y type) for Delphacodes striatella (Araeopidae), 2n = 28 ( female ) for Lysiphlebus sp. (Braconidae) and 2n = 4 ( female ) for Oigosita sp. (Trichogrammidae). There was a remarkable frequency for abnormal cell divisions during the meiosis in D. striatella. The chromosome number of Oigosita sp. was the smallest number (2n = 4) in Hymenoptera.